Proportional throttle valve

ABSTRACT

The invention relates to a proportional throttle valve, comprising a valve piston (2) which has the function of a variable orifice and is displaceably guided in the longitudinal direction in a valve housing (3) having a fluid inlet (4) and a fluid outlet (5). Since a leading edge (6) of the valve piston (2) is formed by a control piston (7) of a flow regulator (8) for the fluidic connection of the fluid inlet (4) and the fluid outlet (5), the flow control valve and the proportional throttle valve are functionally combined in one valve unit.

The invention relates to a proportional throttle valve comprising a valve piston which enables an orifice function and which is movably guided in a valve housing with a fluid inlet and a fluid outlet in the longitudinal direction, the valve piston with a metering edge activating a fluid connection between the fluid inlet and the fluid outlet.

Proportional throttle valves are often used when the level of the fluid flow passing through these valves is to be continuously changed, depending on an existing magnetic current of a coil which activates the valve piston. The opening cross section of the valve seat of the valve piston is dependent on the position of the valve piston. If the coil is supplied with a direct electrical current, a magnetic force which is proportional to the magnetic current forms, as a result of which the valve piston is moved into an open position. Here, in general a spring which is located on the back of the valve piston is tensioned; its spring force counteracts the magnetic force. If an equilibrium is established between the magnetic force and spring force, the valve piston remains in its position.

The proportional throttle valve is largely independent of the pressure level which is to be controlled because the valve piston is pressure-equalized, i.e., a uniformly high pressure acts on the two end surfaces.

Proportional throttle valves are used, for example, in lifting-lowering applications, such as in industrial trucks. To lower the load for these applications, a 2/2-way directional valve is used to represent the basic lifting-lowering motion. At the same time, the proportional throttle valve is used for controlling the volumetric flow.

In proportional throttle valves there is, however, the problem that the volumetric flow is dependent on the differential pressure between the fluid inlet and fluid outlet, so that, for example, in industrial trucks or other lifting means the lowering speed depends on the load which is being moved. Boundary values which could damage the lifting means or the load to be transported in the lowering process can be exceeded. In the prior art, therefore a non-adjustable maximum volumetric flow regulator is connected in series upstream of a proportional throttle valve. The maximum volumetric flow regulator is designed to be passive, and therefore engages only when the maximum lowering rate is exceeded. A hydraulic circuit which is to be set up in this respect according to the prior art is therefore complex and, due to the plurality of components, requires an installation space of corresponding large dimensions.

With respect to this prior art, the object of the invention is to devise a proportional throttle valve which integrates the indicated functions.

This object is achieved by a proportional throttle valve with the features of claim 1 in its entirety.

In that, as specified in the characterizing part of claim 1, a metering edge of the valve piston which regulates the fluid connection between the fluid inlet and the fluid outlet is formed by a control piston of a flow regulator, the function of the flow control valve and of the proportional throttle valve is combined in one valve unit.

Preferred embodiments will become apparent from the dependent claims.

In one especially preferred embodiment, which saves installation space, the control piston of the flow regulator is movably guided in the same bore of the valve housing as the valve piston itself. In this connection, it is especially advantageously provided that the control piston of the flow regulator is guided in the manner of a cascade in an axial bore of the valve piston, and a pertinent required control spring is guided radially both in an axial bore of the control piston and also in an axial bore of the valve piston.

A specified metering orifice of the flow regulator is preferably located on the axial end of the control piston which is adjacent to the fluid inlet, forming a seal in a bottom of the control piston, and forms a fluidic connection into the spring chamber of the control spring. The control piston has radial fluid outlets which in the rest state of the proportional throttle valve completely cover the axial bore for the valve piston, and only when the coil is energized to move the valve piston do the outlets partially or completely cover the radial bores of the valve housing which form the fluid outlet. The proportional throttle valve can be designed to be directly controlled or piloted.

The solution according to the invention is detailed below using the drawings. The figures are schematic and not to scale.

FIG. 1 shows a longitudinal section through a proportional throttle valve according to the invention;

FIG. 2 shows a detail designated as II in FIG. 1.

FIG. 1 shows in a longitudinal section a directly controlled proportional throttle valve 1. In a magnet system housing, there is a magnet system 14, with an armature 16, which is not detailed, being actuatable by means of a DC coil 15. The magnet system 14 is preferably made as a pressing, displacement-controlled proportional magnet system, in the energized state of the DC coil 15 the armature 16 and an actuating member 17 which is dynamically connected to the latter being movable down in the direction of a fluid inlet 4.

The actuating member 17 is dynamically connected to a valve piston 2 which is made as an “orifice piston.” In the de-energized state of the DC coil 15, the armature 16, the actuating element 17, and the valve piston 2 are moved by a spring 18 against a lift stop 19. This corresponds to the closed state of the proportional throttle valve 1, the fluid passage between the fluid inlet 4 and fluid outlet 5 being blocked.

The magnet system housing is made with a cylindrical guide 20 to project into a valve housing 3 and is sealed accordingly. The cylindrical actuating element 17 likewise projects into the cylindrical guide 20 and is detachably and positively connected in it to an extension 21 of the valve piston 2, which extension guides the spring 18 like a mandrel, with permanent contact. The extension 21, after passage through a cylindrical spacer 22 with a bottom 23 which defines the lift stop 19, undergoes transition into the valve piston 2 which is formed as an orifice piston. The lift stop 19 separates the back 24 of the valve piston 2 from its main control section 25.

The main control section 25 is divided in its more or less axial middle into a control piston 7 of a flow regulator 8. The control piston 7 is guided in the same bore 9 as the valve piston 2 and is supported to be able to move in the valve housing via the actuating element 17 as part of the main control section 25. The control piston 7 is moreover guided to be able to move axially in an axial bore 10 of the aforementioned valve piston 2. A control spring 11 which is made as a compression spring is guided in the axial bore 10 over approximately half its length.

The control piston 7 has a further axial bore 12 which is used as a guide for the control spring 11. On its axial end facing the fluid inlet 4, a metering orifice 13 is inserted, in particular screwed, into the control piston 7. The control piston 7 has diametrically opposite radial openings 26 which, in the rest state of the proportional throttle valve 1 shown in FIG. 2, in the sealed position completely cover the wall of the bore 9. As FIG. 2 illustrates in its detail II according to FIG. 1, the fluid outlet 5 is formed by at least two openings 27 which are diametrically inserted in the wall of the bore 9. The metering edge 6 is located on the outside diameter of the control piston 7 and is used to regulate the entire volumetric flow between the fluid inlet 4 and fluid outlet 5 when the DC coil 15 is energized accordingly.

In the operation of the proportional throttle valve 1, the control spring 11 by its pretensioning keeps the distance between the metering orifice 13 and the upper part of the valve piston 2 at a maximum. This state lasts until a maximum possible volumetric flow is reached and the valve works solely as a proportional throttle valve. The metering orifice 13 causes a pressure loss when flow through it takes place, depending on the value of the volumetric flow. This pressure value in turn causes a positioning force in the direction to the control spring 11 until the main control section 25 is likewise shortened by shortening the control spring 11. The metering edge 6 is pushed in the direction of a smaller flow cross section on the fluid outlet 5; in doing so, the pressure loss on the metering orifice 13 in turn drops somewhat until an equilibrium state is established for the volumetric flow. The valve piston 2 then assumes the compensator function and the proportional throttle function.

With the solution according to the invention, therefore the flow regulation function of an external flow regulator can be accommodated directly in the proportional throttle valve so that in this way within the hydraulic circuit a complete additional valve can be omitted. As described, this is achieved by the metering orifice and control spring which are necessary for a constant flow regulator being housed in the control piston of the proportional throttle valve. Here the compensator function, which is likewise necessary for a flow regulator, is assumed by the control piston of the proportional throttle valve itself The described metering edge of the piston therefore at the same time assumes the proportional throttle function and also the compensator function of the flow regulator. 

1. A proportional throttle valve comprising a valve piston (2) which enables an orifice function and which is movably guided in a valve housing (3) with a fluid inlet (4) and fluid outlet (5) in the longitudinal direction, characterized in that a metering edge (6) of the valve piston (2) is formed by a control piston (7) of a flow regulator (8) for fluid connection of the fluid inlet (4) to the fluid outlet (5).
 2. The proportional throttle valve according to claim 1, characterized in that the control piston (7) of the flow regulator (8) is movably guided in the same bore (9) of the valve housing (3) as the valve piston (2).
 3. The proportional throttle valve according to claim 1, characterized in that the control piston (7) of the flow regulator (8) is guided in an axial bore (10) of the valve piston (2) and a control spring (11) is supported radially in the axial bore (10) and also in a further axial bore (12) in the control piston (7).
 4. The proportional throttle valve according to claim 1, characterized in that there is a metering orifice (13) of the flow regulator (8) in the control piston (7).
 5. The proportional throttle valve according to claim 4, characterized in that the metering orifice (13) is located in that end region of the control piston (7) which is facing the fluid inlet (4).
 6. The proportional throttle valve according to claim 1, characterized in that the fluid inlet (4) in the axial direction discharges into the valve housing (3) and the fluid outlet (5) located in the radial perpendicular direction thereto extends through the valve housing (3).
 7. The proportional throttle valve according to claim 1, characterized in that the proportional throttle valve (1) is directly controlled. 